Coating process for producing web form products involving application of electrostatic charges and subsequent charge neutralization

ABSTRACT

A process for producing products in web form comprising at least two layers, in which a composition emerging from an applicator is applied as a layer to a substrate in web form which is guided on a transport means, the application taking place with application of electrostatic charges, and in which the substrate coated with the composition is electrostatically neutralized before departing the applicator, the transport means being provided with an electrically insulating coating.

This application is a 371 of PCT/EP02/13212, filed Nov. 25, 2002, andclaims priority under 35 USC §119 on the basis of German Application No.101 57 883.0, filed Nov. 26, 2001.

The invention relates to a process for producing products in web formcomprising at least two layers, especially adhesive tapes with a carriermaterial atop which an adhesive has been applied.

Work has long been ongoing on producing adhesive tapes without usingsolvents or at least on designing the coating operation and thedownstream steps to be solvent-free. Corresponding products with filmsof adhesive based on synthetic rubbers are known. These products,however, cover only the lower-end performance range of adhesive tapes.

For a number of years it has also been possible to obtain solvent-freeadhesives based on acrylate, which can be processed further as hotmeltadhesives for adhesive tapes. Normally, however, they do not match theshear strengths of acrylate compositions applied from solution. Oneimportant reason for this is that the viscosity of the compositionsduring processing must not become too high, since otherwise theoperations of melting and of coating onto a carrier are too expensivefrom the economic standpoint. The viscosity is determined substantiallyby the length of the molecules. Relatively short chain molecules,however, result in poorer shear strengths. Even crosslinking of theadhesive following its application permits only limited improvement.

In the case of natural rubber adhesive systems, the melting operationcan be avoided if success is achieved in mixing the components of thecomposition without solvent and if the hot composition is supplieddirectly to a coating system. Examples of suitable mixing units includeextruders. In the course of mixing, however, the rubber must not bedegraded any more than slightly, since otherwise the product propertiesare impaired.

In the case of acrylate systems, the melting operation can be avoided byremoving the solvent or water from compositions polymerized in solventsor in water, the removal taking place inline for the purpose of coating.In an appropriate extruder, for example, solvents or water can beremoved by way of vacuum zones.

For the application of high-viscosity compositions, slot dies aresuitable. It is found that they are also suitable for high-viscosityadhering compositions as described above. However, above a relativelylow web speed, air bubbles become included between the adhesive and thesubstrate, which is typically coated on a lay-on roller.

In order to reduce the formation of bubbles in the above task, themarket recommends blowing dies, suction dies, and what are known asvacuum boxes. The aim of using these devices is to raise the force withwhich the composition is pressed against the substrate.

Known from film manufacture (for example, EP 0 920 973 A2) are wire,blade, and needle electrodes, disposed transverse to the web, with whichelectrical charges are applied to the composition that is to be laid on.By this means the composition is pressed by electrostatic forces againsta metal roller. Furthermore, combinations of electrostatic forces andforces by air movement are also used (EP 0 707 940 A2).

For the above-described coating of substrates, the literature reportscomplex solutions, in which before being laid onto the chill roll thesubstrate is charged in multistage upstream processes, partiallydischarged by heating, and cooled, in order finally to obtain uniformcharging of the substrate on the lay-on roller (for example, EP 0 299492 A2).

The maximum level of charge on the substrate in these cases, however, isrelatively low, since as early as on leaving the charging roller it isreduced until the air is no longer ionized, owing to the electricalfield strength resulting from the charge density.

In film manufacture (see for example U.S. Pat. No. 4,997,600 A1) aninsulation for rollers is known in which, before the film is laid on,electrical charges are applied to the insulator layer in order toincrease the press-on forces when the film is laid onto the roller.

If no charges are applied to the insulated roller, then electrostaticpress-on forces during laying-on are greatly attenuated as the insulatorlayer increases in thickness. With the required insulator thicknesseswhich are necessary for sufficient high-voltage resistance for theceramic coatings indicated here, achievable bubble-free coating speedsare drastically lowered.

DE 199 05 935 A1 discloses a method of producing a coating ofsolvent-free pressure sensitive adhesive systems on substrates,especially release-coated substrates, in which

-   the pressure sensitive adhesive system is applied in one or more    layers to a rotating roller by means of an adhesive applicator,-   the pressure sensitive adhesive system on the roller is crosslinked    in an exposure means by high-energy radiation, specifically by means    of electron beams (EB), UV or IR radiation, and-   the roller is contacted with the substrate, so that the pressure    sensitive adhesive system is transferred from the roller to the    substrate, and where appropriate is rolled up.

Typical exposure means employed in the context of the embodiment of themethod that is depicted in said patent include linear cathode systems,scanner systems, and multiple longitudinal cathode systems, whereelectron beam accelerators are concerned.

The acceleration voltages are situated in the range between 40 kV and350 kV, preferably from 80 kV to 300 kV. The output doses range between5 and 150 kGy, in particular from 20 to 90 kGy.

As UV crosslinking units it is possible in particular to employ twomedium pressure mercury lamps each with an output of 120 W/cm or onemedium pressure mercury lamp having an output of 240 W/cm. The doses setare preferably from 10 to 300 mJ/cm².

DE 199 05 935 A1 describes a method of producing a coating ofsolvent-free pressure sensitive adhesive systems on substrates,especially release-coated substrates, in which

-   a fluid film is applied to a rotating roller by means of a fluid    applicator,-   the pressure sensitive adhesive system is applied in one or more    layers to the fluid film by means of an adhesive applicator, so that    the fluid film is located between roller and pressure sensitive    adhesive system, and-   the roller is contacted with the substrate, so that the pressure    sensitive adhesive system is transferred from the roller to the    substrate (release-coated or otherwise).    The contacting of the substrate takes place in particular by way of    a second roller. Substrates used include papers, films, nonwovens,    and release-coated materials such as release papers, films, and the    like.

The second roller, also referred to as a contact roller, may have beenprovided with a rubber coating and is pressed against the roller with alinear pressure of preferably 50 to 500 N/mm, in particular from 100 to200 N/mm. The contact roller preferably has a Shore hardness (A) of from40 to 100, in particular a Shore hardness of from 60 to 80 shore (A).The substrate is preferably brought into contact with the roller in sucha way that the speed of the roller surface coincides with that of thesubstrate. Where, however, it is intended that a reduction in thicknessshould take place along with the removal of the adhesive film, thesubstrate may also have a higher speed.

In one advantageous embodiment the roller is a steel roller, achrome-plated steel roller, a rubber roller or a silicone rubber rollerand/or is manufactured from elastic material. Furthermore, the rollermay be smooth or may have a slightly structured surface.

The smooth roller may preferably have a chrome coating. Optionally, thechrome-coated steel roller may possess a high-gloss-polished surfacewith a roughness R_(z)<0.02 μm. The coating roller may also, however, berubberized, preferably with a rubber hardness of from 40 to 100 shore(A), in particular with a hardness of from 60 to 80 shore (A). Theroller coating may, in accordance with the prior art, comprise EPDM,Viton or silicone rubber, or other elastic materials.

It has also proven advantageous for the roller to betemperature-controllable, preferably in a range from −10° C. to 200° C.,in particular from 2° C. to 50° C.

If substrates treated antiadhesively on one or both sides with very thincoats are coated, for the production of adhesive tapes, with anadhesive, then the release effect of the substrate, particularly withrespect to acrylate adhesives, is impaired if the laying-on of theadhesive is assisted electrostatically with high-voltage electrodes.

It is an object of the invention to allow the substrate to be coatedwith compositions, especially compositions of high viscosity, such asare used for producing adhesive tapes or similar products, with thepreferred use of a slot die, with sufficiently high web speeds. In thecourse of this operation, there should be

-   no bubbles included between the composition coat and the substrate,-   no detriment to quality-critical properties of the product being    produced, and-   no hazards arising for operating staff.

This object is achieved by means of a process as specified in the mainclaim. The subclaims describe advantageous embodiments of the process.

The invention accordingly provides a process for producing products inweb form having at least two layers, in which a composition emergingfrom an application means is applied to a substrate in web form which isguided on a transport means, said application taking place withapplication of electrostatic charges, and in which the substrate coatedwith the composition is electrostatically neutralized before departingthe transport means, the transport means being provided with anelectrically insulating coating for reducing damage.

In a first preferred embodiment of the process the application means isconfigured as a die, particularly a slot die, two-manifold ormultiple-manifold die or adaptor die.

The transport means is coated, preferably contactlessly, with thecomposition emerging from the die. The distance of the die from thetransport means may be preferably from 0.01 to 60 mm, in particular from1 to 30 mm.

With further preference, the transport means is designed as a lay-onroller, which additionally, in particular, is of a grounded and/ortemperature-controllable design, i.e., preferably in a range of from−10° C. to 200° C., very preferably in a range of from 0° C. to 180° C.,in particular from 2° C. to 50° C.

In order to be able to provide the composition with the charge accordingto the invention, the composition may be charged electrostatically bymeans of at least one charging electrode, called lay-on electrode below,which is located in particular above the transport means, preferablylay-on roller, and specifically in the region of the lay-on line of thecomposition coat. The coat is pressed onto the substrate with the aid ofthe charges.

With the lay-on electrode, charges—electrons, for example—are applied toone side of the composition. On the surface of the transport means,preferably lay-on roller, countercharges come about immediately. Theresulting field causes a force to act on the composition plus substrate,which presses both coats onto the transport means, preferably lay-onroller.

Moreover, in one outstanding embodiment of the inventive concept, thesubstrate coated with the composition is electrostatically neutralizedby means of at least one countercharging electrode prior to departingthe transport means, preferably lay-on roller, said counterchargingelectrode very particularly being located over the transport means,preferably lay-on roller, in the region between the lay-on line of thecomposition coat and the take-off line of the coated substrate.

Accordingly, electrostatic discharges as a consequence of applyingcharges by the lay-on electrode can be prevented even before the coatedsubstrate has departed the preferred lay-on roller, by applyingcountercharges of opposite polarity and appropriate size.

For fine tuning it is further advantageous to mount an active dischargemeans over the detachment line of the coated substrate from thepreferred lay-on roller, in order to compensate process-relatedfluctuations over time and across the width of the web.

The countercharging electrode is preferably in the form of a wireelectrode, blade electrode and/or needle electrode which is disposedtransverse to the web.

Without adequate neutralization of the electrical charges applied to theweb by the lay-on electrode(s), there may be a corona discharge betweenthe lay-on roller and the underside of the substrate, which mayadversely affect, in particular, anti-adhesive properties of thesubstrate.

Additionally, as a result of the corona discharge, charges of opposedpolarity may be transported on the underside of the web as on thecoating side. If such a web is subsequently neutralized with customaryactive or passive discharge means, the measurable electrical field iseliminated but afterward there are still very strong, equally highcharges of opposed polarity on the two sides. If the electricalconductivity of the coats between the charges is low, there may beuncontrollable discharges in bales that have been wound up.

In order to subject the substrate to as little stress as possible, thesubstrate should then be placed onto the transport means, preferablylay-on roller, with a contact roller and/or removed from the transportmeans, preferably lay-on roller, with a take-off roller.

It is advantageous, additionally, to select a conductive elastic coatingas the preferred roller with which the substrate is placed onto thepreferably selected lay-on roller. Where a conductive coating cannot beused for technical reasons associated with the process, it isadvantageous to subject the roller jacket to electrostatic discharge ina region in which it is not covered by the substrate. Otherwise, witheach turn the roller surface may pick up more and more electricalcharges, until uncontrolled discharge phenomena occur.

It is also advantageous to dispose a baffle of electrically insulatingmaterial in the running direction of the web upstream of the lay-onelectrode, thereby limiting the ion-enriched area in the region of thelay-on electrode on the die side. It is favorable, in addition, to mounta grounded, electrically conducting metal plate on the side of thebaffle that faces away from the lay-on electrode. By means of thebaffle, any corona discharge upstream of the lay-on line can be reducedmarkedly by the composition coat on the substrate.

Also of advantage is an arrangement in which not only one needleelectrode is used as lay-on electrode but instead two, directlyfollowing one another in the web direction, the two electrodes beingoffset laterally by half a needle spacing, thereby pairing the capacityof the needle electrodes for high charging currents with a relativelyuniform charge distribution. In this context it has been foundadvantageous to impose a smaller high voltage on the front electrodethan on the rear electrode.

In another preferred embodiment of the invention, the substrate iselectrostatically neutralized prior to coating.

In another preferred variant of the process of the invention, thecomposition on the substrate is crosslinked or polymerized beforedeparting the transport means, preferably lay-on roller, in particularby means of electron beams, UV rays, visible light or thermally or elseby means of a combination of said processes.

In another preferred embodiment of the process, the thickness of thecoating is less than 300 μm, in particular between 20 and 200 μm, veryparticularly between 20 and 120 μm and/or does not deviate more thanpreferably ±20% from the average value, in particular not more than ±5%,over the entire substrate-contact surface of the transport means.

It is also very advantageous if the coating has a low roughness and/orantiadhesive properties.

A particularly advantageous measure is to effect electrostaticneutralization of the coating in an area in which it is not covered bythe substrate before it becomes covered by the substrate. Otherwise,with each revolution, it may pick up electrical charges more and moreuntil uncontrolled discharge phenomena occur. However, even relativelyminor uncontrolled charging, especially if it occurs nonuniformly, hasan adverse effect on the formation of bubbles between coating andsubstrate.

In one outstanding embodiment, the coating is composed of polyester,TEFLON (polytetrafluoroethylene), CAPTON (polyimide), silicone rubber,polypropylene, casting resin or other materials which have sufficienthigh-voltage resistance at low coat thickness.

As a coating it is possible, for example, to use a shrink sleeve, whichis pulled over the transport means, especially a lay-on roller, andshrunk.

Also outstandingly suitable is an insulator-coated, electricallyconductive sleeve which is pulled over the transport means, especiallylay-on roller.

In one preferred variant of the process the coating is applied inexcess, is cured where appropriate, is additionally removed subsequentlydown to a desired, highly constant layer thickness, and then, finally,is polished for low roughness.

Examples that may be mentioned of possible embodiments of the coatinginclude PET films of different thicknesses, and also applications ofcasting resin, preferably with thicknesses of between 20 μm and 300 μmand in particular with thicknesses of between 20 μm and 120 μm.

Another preferred variant is constituted by an electrically conductiveconveyor belt which is coated with an electrical insulator and on whichthe substrate, for the purpose of coating, is guided over a lay-onroller; it being possible for the coating to have thicknesses ofpreferably between 20 μm and 300 μm and in particular between 20 μm and120 μm.

Another preferred variant is a thin conveyor belt comprising anelectrical insulator, preferably with thicknesses of between 20 μm and300 μm and in particular with thicknesses of between 20 μm and 120 μm,on which the substrate, for the purpose of coating, is guided over alay-on roller.

Another preferred variant is a modification wherein an auxiliary sheet,inserted between the electrically conductive transport means and thesubstrate following unwinding from a bale, is wound to a bale againafter the coated substrate has been removed from the auxiliary sheet.

The process can be used to outstanding effect in those applicationswhere the substrate is a release liner for an adhesive tape and/or thecomposition is an adhesive.

In this case the composition used may also comprise acrylic, naturalrubber, synthetic rubber or EVA adhesives.

The process can likewise be used to outstanding effect in thoseapplications where the substrate is a preliminary product comprisingrelease liner, adhesive composition and carrier for a double-sidedadhesive tape and the composition is an adhesive.

Furthermore, it is found that the tendency to form bubbles between thecomposition and the substrate increases if the substrate has becomecharged in an uncontrolled manner prior to placement onto the lay-onroller. It is also a problem if electrostatic discharge means are notmounted on the side of the web on which charging can take place as aresult of separation events. In this case as well, no electrical fieldis measured any longer from the outside, but nevertheless there areequally strong electrical charges of opposed polarity on both sides ofthe web. The level of these double charges typically fluctuates in theweb direction and also transversely to the web. These undefined doublecharges reduce the maximum speed at which the web can be effectively andsafely run in a production process.

In one advantageous embodiment, discharge means are always mounted onthe side at which charges occur as a result of separation events. Withelectrostatically difficult substrates, it may in extreme cases be ofadvantage to mount suitable discharge means behind each deflectingroller on the contact side and even in the winding nip at the unwindstage.

Moreover, it is advantageous to run the supplied bales with thesubstrate under electrostatic control as early as in the upstreamprocess, or to select a sufficiently long interim storage period, due tosufficient electrical residual conductivities, for double charges toflow together. The time required may also be shortened by means ofstorage at elevated temperatures.

It is particularly advantageous to mount a baffle made of electricallyinsulating material in the running direction of the web between theapplicator and the lay-on electrode, thereby bordering the ion-filledarea in the region of the lay-on electrode by the applicator, especiallydie, the transport means, especially lay-on roller, and the baffle.

It is also possible for the coating to be composed of one or more layersand/or for the substrate to be composed of one or more layers, it beingadvantageous to produce multilayer coatings using multiple-manifold oradaptor dies.

It is also very advantageous if, using adaptors in the case of asingle-manifold die or using a triple-manifold die, a coating composedof a first adhesive, a carrier, and a second adhesive is extruded andthe substrate is a release liner.

Unexpectedly for the skilled worker, the inventive process offers asolution to the problems posed. Thus, coating with a slot die onto asubstrate at sufficiently high web speeds is made possible without thedevelopment of bubbles between the composition coat and the substrate,without adverse effects on other, quality-critical properties of theproduct to be produced, in particular separating properties of releaseliners, and without special risks to the operating staff.

Surprisingly it has been found that bubbles are formed between thecomposition coat and the substrate particularly when there is airbetween the substrate and the lay-on roller. If the substrate was placedonto the lay-on roller in a bubble-free manner, it was possible to carryout coating with a higher web speed without the formation of bubbles.The appearance of the coating is much more uniform than in the case of acoating operation in which the substrate was not placed bubble-free onthe lay-on roller during the production process.

Moreover, it is possible to ascertain, unexpectedly, that the formationof bubbles between the composition coat and the substrate is greatlyreduced if the substrate is electrostatically neutralized in the webregion upstream of the lay-on roller, very preferably on the side atwhich a charge accumulation occurs as a result of charge separationevents.

With further preference, the substrate present on the transport meanscan be crosslinked, between the lay-on electrode and dischargeelectrode, by means of high-energy radiation supplied by an irradiationmeans, specifically by means of electron beams (EB), UV or IR rays. Thisis especially advantageous when the substrate in question is anadhesive.

Typical exposure means employed in the context of the inventiveembodiment of the process are linear cathode systems, scanner systems,or multiple longitudinal cathode systems, where electron beamaccelerators are concerned.

The acceleration voltages are situated preferably in the range between40 kV and 500 kV, in particular between 80 kV and 300 kV. The outputdoses range between 5 and 150 kGy, in particular from 15 to 90 kGy.

As UV crosslinking units it is possible in particular to employ one ormore medium pressure mercury lamps each with an output of up to 240 W/cmper lamp. The doses set are preferably from 10 to 300 mJ/cm².

For crosslinking or polymerization with visible light, halogen lamps maybe employed in particular.

As substrate it is also possible to use release liners withanti-adhesive coatings to which the adhesion of adhesives is low. Thebacking materials of release liners are typically composed of paper orplastics, such as PET, PP or else PE, for example. The plastics usedgenerally have good electrical insulation properties and high electricalbreakdown field strengths.

In the case of papers, in contrast, the electrical properties aredetermined substantially by the thin anti-adhesive coating, but also bythe impregnation and the moisture content. When the composition isapplied with assistance by electrostatic charging, greater importanceattaches to the electrical properties of the applied composition.Although the compositions employed are usually electrical insulators,their residual conductivity at typical coating temperatures of 100° C.or more is often already sufficiently high for some of the appliedcharges to flow off through the composition and through the paperrelease liner into the lay-on roller before departing the roller. Sinceat the lay-on line, if the electrical conductivity is not too high,virtually all of the charge is still present on the composition coat, itis nevertheless possible to achieve sufficiently high pressing forcesfor bubble-free coating. In the subsequent electrical neutralization bythe application of countercharges, however, it must be borne in mindthat some of the charge has already flowed off. At low web speeds, thetime available for the charges to flow off becomes greater, andproportionally more charge flows off before the detachment line isreached. The optimum level of the countercharges is therefore dependenton the web speed.

For reasons of both economics and processing, the release coatings usedfor release liners are as thin as possible. Use is also made of whathave been dubbed “substituted-covering coatings”. By this is meant thatthe carrier is not hidden 100% by the release coating. It has been foundthat neutralization of the coated substrate in the case of such releaseliners must be carried out with substantially greater precision than isthe case, say, with PET or PP films with fully hiding silicone coatingsof 1.5 g/m² or more.

In the cases of double-sided adhesive tapes, a distinction is madebetween the open side and the hidden side of the release liner. Thehidden side of the release liner, after being unwound from the roll, iscovered with the assembly comprising first adhesive film, carrier, andsecond adhesive film. For undisrupted further processing after coatingand until application, the release forces from the adhesive on the openside should be less than or equal to, and at least not substantiallygreater than, release forces on the hidden side, since otherwise theremay be a reorientation of the release liner to the other side.

Graded release liners are also available. With these, it can be ensuredthat the hidden side has much higher release forces.

In the case of non-graded release liners, in particular, damage to theopen side when producing a double-sided adhesive tape must only berelatively low, since the desire is to avoid replacement by an undamagedrelease liner.

For the production of double-sided adhesive tapes, the substrate mayalso be composed of the initial product from the first operation, namelyof a release liner, an adhesive film, and the carrier.

As substrate or carrier material it is possible to use all known textilecarriers such as wovens, knits, lays or nonwoven webs; the term “web”embraces at least textile sheetlike structures in accordance with EN29092 (1988) and also stitchbonded nonwovens and similar systems.

It is likewise possible to use spacer fabrics, including wovens andknits, with lamination. Spacer fabrics of this kind are disclosed in EP0 071 212 B1. Spacer fabrics are matlike layer structures comprising acover layer of a fiber or filament fleece, an underlayer and individualretaining fibers or bundles of such fibers between these layers, saidfibers being distributed over the area of the layer structure, beingneedled through the particle layer, and joining the cover layer and theunderlayer to one another. As an additional though not mandatoryfeature, the retaining fibers in accordance with EP 0 071 212 B1comprise inert mineral particles, such as sand, gravel or the like, forexample.

The holding fibers needled through the particle layer hold the coverlayer and the underlayer at a distance from one another and are joinedto the cover layer and the underlayer.

Spacer wovens or spacer knits are described, inter alia, in twoarticles, namely

-   -   an article from the journal kettenwirk-praxis 3/93, 1993, pages        59 to 63, “Raschelgewirkte Abstandsgewirke” [Raschel-knitted        spacer knits] and    -   an article from the journal kettenwirk-praxis 1/94, 1994, pages        73 to 76, “Raschelgewirkte Abstandsgewirke”,        the content of said articles being included here by reference        and being part of this disclosure and invention.

Knitted fabrics are produced from one or more threads or thread systemsby intermeshing (interlooping), in contrast to woven fabrics, which areproduced by intersecting two thread systems (warp and weft threads), andnonwovens (bonded fiber fabrics), where a loose fiber web isconsolidated by heat, needling or stitching or by means of water jets.

Knitted fabrics can be divided into weft knits, in which the threads runin transverse direction through the textile, and warp knits, where thethreads run lengthwise through the textile. As a result of their meshstructure, knitted fabrics are fundamentally pliant, conformingtextiles, since the meshes are able to stretch lengthways and widthways,and have a tendency to return to their original position. In high-gradematerial, they are very robust.

Suitable nonwovens include, in particular, consolidated staple fiberwebs, but also filament webs, meltblown webs, and spunbonded webs, whichgenerally require additional consolidation. Known consolidation methodsfor webs are mechanical, thermal, and chemical consolidation. Whereaswith mechanical consolidations the fibers can be held together purelymechanically by entanglement of the individual fibers, by theinterlooping of fiber bundles or by the stitching-in of additionalthreads, it is possible by thermal and by chemical techniques to obtainadhesive (with binder) or cohesive (binderless) fiber-fiber bonds. Givenappropriate formulation and an appropriate process regime, these bondsmay be restricted exclusively, or at least predominantly, to the fibernodal points, so that a stable, three-dimensional network is formedwhile retaining the loose open structure in the web.

Webs which have proven particularly advantageous are those consolidatedin particular by overstitching with separate threads or by interlooping.

Consolidated webs of this kind are produced, for example, onstitchbonding machines of the “Malifleece” type from the company KarlMeyer, formerly Malimo, and can be obtained, inter alia, from thecompanies Naue Fasertechnik and Techtex GmbH. A Malifleece ischaracterized in that a cross-laid web is consolidated by the formationof loops from fibers of the web.

The carrier used may also be a web of the Kunit or Multiknit type. AKunit web is characterized in that it originates from the processing ofa longitudinally oriented fiber web to form a sheetlike structure whichhas the heads and legs of loops on one side and, on the other, loop feetor pile fiber folds, but possesses neither threads nor prefabricatedsheetlike structures. A web of this kind has been produced, inter alia,for many years, for example on stitchbonding machines of the“Kunitvlies” type from the company Karl Mayer. A further characterizingfeature of this web is that, as a longitudinal-fiber web, it is able toabsorb high tensile forces in the longitudinal direction. Thecharacteristic feature of a Multiknit web relative to the Kunit is thatthe web is consolidated on both the top and bottom sides by virtue ofthe double-sided needle punching.

Finally, stitchbonded webs are also suitable as an intermediate formingan adhesive tape. A stitchbonded web is formed from a nonwoven materialhaving a large number of stitches extending parallel to one another.These stitches are brought about by the incorporation, by stitching orknitting, of continuous textile threads. For this type of web,stitchbonding machines of the “Maliwatt” type from the company KarlMayer, formerly Malimo, are known.

Also particularly advantageous is a staple fiber web which ismechanically preconsolidated in the first step or is a wet-laid web laidhydrodynamically, in which between 2% and 50% of the web fibers arefusible fibers, in particular between 5% and 40% of the fibers of theweb.

A web of this kind is characterized in that the fibers are laid wet or,for example, a staple fiber web is preconsolidated by the formation ofloops from fibers of the web or by needling, stitching or air-jet and/orwater-jet treatment.

In a second step, thermofixing takes place, with the strength of the webbeing increased again by the (partial) melting of the fusible fibers.

The web carrier may also be consolidated without binders, by means forexample of hot embossing with structured rollers, with properties suchas strength, thickness, density, flexibility, and the like beingcontrollable via the pressure, temperature, residence time, andembossing geometry.

For the use of nonwovens, the adhesive consolidation of mechanicallypreconsolidated or wet-laid webs is of particular interest, it beingpossible for said consolidation to take place by way of the addition ofbinder in solid, liquid, foamed or pastelike form. A great diversity oftheoretical embodiments is possible: for example, solid binders aspowders for trickling in; as a sheet or as a mesh, or in the form ofbinding fibers. Liquid binders may be applied as solutions in water ororganic solvent or as a dispersion. For adhesive consolidation, binderdispersions are predominantly chosen: thermosets in the form of phenolicor melamine resin dispersions, elastomers as dispersions of natural orsynthetic rubbers, or, usually, dispersions of thermoplastics such asacrylates, vinyl acetates, polyurethanes, styrene-butadiene systems,PVC, and the like, and also copolymers thereof. Normally, thedispersions are anionically or nonionically stabilized, although incertain cases cationic dispersions may also be of advantage.

The binder may be applied in a manner which is in accordance with theprior art and for which it is possible to consult, for example, standardworks of coating or of nonwoven technology such as “Vliesstoffe” (GeorgThieme Verlag, Stuttgart, 1982) or “Textiltechnik-Vliesstofferzeugung”(Arbeitgeberkreis Gesamttextil, Eschborn, 1996).

For mechanically preconsolidated webs which already possess sufficientcomposite strength, the single-sided spray application of a binder isappropriate for effecting specific changes in the surface properties.

Such a procedure is not only sparing in its use of binder but alsogreatly reduces the energy requirement for drying. Since no squeezerollers are required and the dispersion remains predominantly in theupper region of the web material, unwanted hardening and stiffening ofthe web can very largely be avoided.

For sufficient adhesive consolidation of the web carrier, the additionof binder in the order of magnitude of from 1% to 50%, in particularfrom 3% to 20%, based on the weight of fiber web, is generally required.

The binder may be added as early as during the manufacture of the web,in the course of mechanical preconsolidation, or else in a separateprocess step, which may be carried out in-line or off-line. Followingthe addition of the binder it is necessary temporarily to generate acondition in which the binder becomes adhesive and adhesively connectsthe fibers—this may be achieved during the drying, for example, ofdispersions, or else by heating, with further possibilities forvariation existing by way of areal or partial application of pressure.The binder may be activated in known drying tunnels, or else, given anappropriate selection of binder, by means of infrared radiation, UVradiation, ultrasound, high-frequency radiation or the like. For thesubsequent end use it is sensible, although not absolutely necessary,for the binder to have lost its tack following the end of the webproduction process. It is advantageous that, as a result of the thermaltreatment, volatile components such as fiber assistants are removed,giving a web having favorable fogging values so that when a low-foggingadhesive is used it is possible to produce an adhesive tape havingparticularly advantageous fogging values.

A further, special form of adhesive consolidation consists in activatingthe binder by incipient dissolution or swelling. In this case it is alsopossible in principle for the fibers themselves, or admixed specialfibers, to take over the function of the binder. Since, however, suchsolvents are objectionable on environmental grounds, and/or areproblematic in their handling, for the majority of polymeric fibers,this process is not often employed.

Starting materials envisaged for the textile carrier include, inparticular, polyester, polypropylene, viscose or cotton fibers. Theselection is, however, not restricted to said materials; rather it ispossible to use a large number of other fibers to produce the web, thisbeing evident to the skilled worker without any need for inventiveactivity.

Carrier materials used further include, in particular, laminates andnets, and also films (for example, a polyolefin from the group of thepolyethylenes (for example, HDPE, LDPE, MDPE, LLDPE, VLLDPE, copolymersof ethylene with polar comonomers) and/or the group of thepolypropylenes (for example, polypropylene homopolymers, randompolypropylene copolymers or block polypropylene copolymers), monoaxiallyor biaxially oriented polypropylene, polyesters, PVC, PET, polystyrene,polyamide or polyimide), foams, foam material, of polyethylene andpolyurethane, for example, foamed films, and creped and uncreped paper.Moreover, these materials may have been given a pretreatment and/or anaftertreatment. Common pretreatments are corona irradiation,impregnation, coating, painting, and hydrophobicization; customaryaftertreatments are calendering, thermal conditioning, lamination, diecutting, and enveloping.

Low flammability in the carrier material and in the adhesive tape as awhole may be achieved by adding flame retardants to the carrier and/orto the adhesive. These retardants may be organobromine compounds,together where appropriate with synergists such as antimony trioxide;however, with a view to the absence of halogens from the adhesive tape,preference will be given to using red phosphorus, organophosphoruscompounds, mineral compounds or intumescent compounds such as ammoniumpolyphosphate, alone or in conjunction with synergists.

As adhesives it is possible to use substantially all known adhesivespossessing sufficient bond strength to the bond substrate that is to bepacked.

The adhesive of the adhesive tape may be composed of an adhesive basedon solventborne natural rubber adhesives and acrylic adhesives.Preference is given to adhesives based on acrylic dispersions; adhesivesbased on styrene-isoprene-styrene block copolymers are particularlypreferred. These adhesive technologies are known and are used in theadhesive tape industry.

The coatweight of the adhesive on the carrier material is preferablyfrom 15 to 60 g/m². In a further preferred embodiment, the coatweightset is from 20 to 30 g/m².

The adhesive tapes can be produced by known methods. An overview ofcustomary production methods can be found, for example, in “CoatingEquipment”, Donatas Satas in Handbook of Pressure Sensitive AdhesiveTechnology, second edition, edited by Donatas Satas, Van NostrandReinhold New York pp. 767–808. The known methods of drying and slittingthe adhesive tapes are likewise to be found in the Handbook of PressureSensitive Adhesive Technology, pp. 809–874.

A suitable adhesive composition is one based on acrylic hotmelt, havinga K value of at least 20, in particular more than 30 (measured in eachcase in 1% strength by weight solution in toluene at 25° C.), obtainableby concentrating a solution of such a composition to give a system whichcan be processed as a hotmelt.

Concentrating may take place in appropriately equipped vessels orextruders; particularly in the case of accompanying devolatilization, adevolatilizing extruder is preferred.

An adhesive of this kind is set out in DE 43 13 008 C2. In anintermediate step, the solvent is removed completely from the acrylatecompositions prepared in this way.

The K value is determined in particular in analogy to DIN 53 726.

In addition, further volatile constituents are removed. After coatingfrom the melt, these compositions contain only small fractions ofvolatile constituents. Accordingly, it is possible to adopt all of themonomers/formulations claimed in the above-cited patent. A furtheradvantage of the compositions described in the patent is that they havea high K value and thus a high molecular weight. The skilled worker isaware that systems with higher molecular weights may be crosslinked moreefficiently. Accordingly, there is a corresponding reduction in thefraction of volatile constituents.

The solution of the composition may contain from 5 to 80% by weight, inparticular from 30 to 70% by weight, of solvent.

It is preferred to use commercially customary solvents, especiallylow-boiling hydrocarbons, ketones, alcohols and/or esters.

Preference is further given to using single-screw, twin-screw ormultiscrew extruders having one or, in particular, two or moredevolatilizing units.

The adhesive based on acrylic hotmelt may contain copolymerized benzoinderivatives, such as benzoin acrylate or benzoin methacrylate, forexample, acrylates or methacrylates. Benzoin derivatives of this kindare described in EP 0 578 151 A.

The adhesive based on acrylic hotmelt may be UV-crosslinked. Other typesof crosslinking, however, are also possible, an example being electronbeam crosslinking.

In one particularly preferred embodiment, self-adhesive compositionsused comprise copolymers of (meth)acrylic acid and esters thereof havingfrom 1 to 25 carbon atoms, maleic, fumaric and/or itaconic acid and/oresters thereof, substituted (meth)acrylamides, maleic anhydride, andother vinyl compounds, such as vinyl esters, especially vinyl acetate,vinyl alcohols and/or vinyl ethers.

The residual solvent content should be below 1% by weight.

It is also possible to use an adhesive from the group of the naturalrubbers or the synthetic rubbers or any desired blend of natural and/orsynthetic rubbers, the natural rubber or rubbers being selectable inprinciple from all available grades such as, for example, crepe, RSS,ADS, TSR or CV grades, depending on required purity and viscosity, andthe synthetic rubber or rubbers being selectable from the group ofrandomly copolymerized styrene-butadiene rubbers (SBR), butadienerubbers (BR), synthetic polyisoprenes (IR), butyl rubbers (IIR),halogenated butyl rubbers (XIIR), acrylic rubbers (ACM), ethylene-vinylacetate (EVA) copolymers and polyurethanes and/or blends thereof.

Furthermore, and preferably, the processing properties of the rubbersmay be improved by adding to them thermoplastic elastomers with a weightfraction of from 10 to 50% by weight, based on the total elastomerfraction.

As representatives, mention may be made at this point, in particular, ofthe particularly compatible styrene-isoprene-styrene (SIS) andstyrene-butadiene-styrene (SBS) types.

As tackifying resins it is possible without exception to use all knowntackifier resins which have been described in the literature.Representatives that may be mentioned include the rosins, theirdisproportionated, hydrogenated, polymerized, esterified derivatives andsalts, the aliphatic and aromatic hydrocarbon resins, terpene resins,and terpene-phenolic resins. Any desired combinations of these and otherresins may be used in order to adjust the properties of the resultingadhesive in accordance with what is desired. Explicit reference is madeto the depiction of the state of the art in the “Handbook of PressureSensitive Adhesive Technology” by Donatas Satas (van Nostrand, 1989).

“Hydrocarbon resin” is a collective term for thermoplastic polymerswhich are colorless to intense brown in color and have a molar mass ofgenerally <2000.

They may be divided into three main groups according to theirprovenance: petroleum resins, coal tar resins, and terpene resins. Themost important coal tar resins are the coumarone-indene resins. Thehydrocarbon resins are obtained by polymerizing the unsaturatedcompounds that can be isolated from the raw materials.

Included among the hydrocarbon resins are also polymers obtainable bypolymerizing monomers such as styrene and/or by means ofpolycondensation (certain formaldehyde resins), with a correspondinglylow molar mass. Hydrocarbon resins are products with a softening rangethat varies within wide limits from <0° C. (hydrocarbon resins liquid at20° C.) to >200° C. and with a density of from about 0.9 to 1.2 g/cm³.

They are soluble in organic solvents such as ethers, esters, ketones,and chlorinated hydrocarbons, and are insoluble in alcohols and water.

By rosin is meant a natural resin which is recovered from the cruderesin from conifers.

Three types of rosin are differentiated: balsam resin, as a distillationresidue of turpentine oil; root resin, as the extract from conifer rootstocks; and tall resin, the distillation residue of tall oil. The mostsignificant in terms of quantity is balsam resin.

Rosin is a brittle, transparent product with a color ranging from red tobrown. It is insoluble in water but soluble in many organic solventssuch as (chlorinated) aliphatic and aromatic hydrocarbons, esters,ethers, and ketones, and also in plant oils and mineral oils. Thesoftening point of rosin is situated within the range from approximately70 to 80° C.

Rosin is a mixture of about 90% resin acids and 10% neutral substances(fatty acid esters, terpene alcohols, and hydrocarbons). The principalrosin acids are unsaturated carboxylic acids of empirical formulaC₂₀H₃₀O₂, abietic, neoabietic, levopimaric, pimaric, isopimaric, andpalustric acid, as well as hydrogenated and dehydrogenated abietic acid.The proportions of these acids vary depending on the provenance of therosin.

Plasticizers which can be used are all plasticizing substances knownfrom adhesive tape technology. They include, inter alia, the paraffinicand naphthenic oils, (functionalized) oligomers such as oligobutadienesand oligoisoprenes, liquid nitrile rubbers, liquid terpene resins,animal and vegetable oils and fats, phthalates, and functionalizedacrylates.

For the purpose of heat-induced chemical crosslinking, it is possible touse all known heat-activatable chemical crosslinkers such as acceleratedsulfur or sulfur donor systems, isocyanate systems, reactive melamineresins, formaldehyde resins, and (optionally halogenated)phenol-formaldehyde resins and/or reactive phenolic resin ordiisocyanate crosslinking systems with the corresponding activators,epoxidized polyester resins and acrylic resins, and combinationsthereof.

The crosslinkers are preferably activated at temperatures above 50° C.,in particular at temperatures from 100° C. to 160° C., with veryparticular preference at temperatures from 110° C. to 140° C.

The thermal excitation of the crosslinkers may also be effected by meansof IR rays or other high-energy electromagnetic alternating fields.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the figures described below, particularly advantageousembodiments of the invention are illustrated, without wishing to beunnecessarily restricted by the choice of the figures shown.

FIG. 1 shows the process of the invention in one particularlyadvantageous embodiment, and

FIG. 2 shows the process of the invention in a second particularlyadvantageous embodiment.

Accordingly, FIG. 1 shows a device in which an adhesive 8 is placed ontoa substrate 7. That is, it shows a process for producing adhesive tapes.

The device has a lay-on roller 6 with a thin electrically insulatingcoating 10. In this case, a grounded chill roll is used. The substrate 7is a release liner, consisting of a monoaxially oriented polypropylenefilm provided on both sides with anti-adhesive silicone layers. Thecoating 10 is intended to reduce damage to the antiadhesive siliconelayers caused by the electrostatic laying-on.

The substrate 7 is placed onto the lay-on roller 6 with an electricallyinsulating coating 10 via a contact roller 4, thereby removing the airbetween substrate 7 and lay-on roller 6. Finally, via the coating die 5,the composition 8, in this case an adhesive, is applied, this operationbeing carried out under the lay-on electrode 1.

Here, with the lay-on electrode 1, ions are applied to one side of thecomposition 8. Countercharges immediately develop below the electricallyinsulating coating 10 of the lay-on roller 6. The resulting field causesa force to act on the composition plus substrate, this force pressingboth layers onto the lay-on roller 6.

After it has traversed the countercharging electrode 2 and the dischargeelectrode 3, the substrate 7 coated with the composition 8 is removedfrom the lay-on roller 6.

The countercharging electrode 2 brings opposite charges, such as thecharging electrode, to the composition 8, so that the charges largelyneutralize each other.

At the discharge electrode 3, finally, the last charges on thecomposition 8 are removed.

The baffle 9 upstream of the lay-on electrode 1 bounds the ion-enrichedspace.

The lay-on roller 6 is provided with an insulating coating 10, in thiscase a PET casting resin.

The discharge electrode 11 is intended to prevent charging of theinsulator coat 10.

FIG. 2 shows a device in which an adhesive 8 is placed onto a substrate7. That is, it shows a process for producing adhesive tapes.

The device has a lay-on roller 6, over which there runs an electricallyconductive conveyor belt 10 with a thin, electrically insulatingcoating. A grounded chill roll is used. The substrate 7 is a releaseliner, consisting of a release paper provided on both sides withantiadhesive silicone layers. The conveyor belt 10 with an electricallyinsulating coating is intended to reduce the damage to the antiadhesivesilicone layers caused by the electrostatic laying-on.

The substrate 7 is placed onto the lay-on roller 6 via a contact roller4, with the conveyor belt 10 between them. Finally, via the coating die5, the composition 8, in this case an adhesive, is applied, thisoperation being carried out under the lay-on electrode 1.

Here, with the lay-on electrode 1, ions are applied to one side of thecomposition 8. Countercharges immediately develop under the electricallyinsulating coating of the conveyor belt 10 which is grounded by way ofthe lay-on roller. The resulting field causes a force to act on thecomposition plus substrate, this force pressing both layers onto theconveyor belt 10.

After it has traversed the countercharging electrode 2 and the dischargeelectrode 3, the substrate 7 coated with the composition 8 is removedfrom the lay-on roller 6.

The countercharging electrode 2 applies opposite charges to thecomposition 8, with the consequence that the charges neutralize oneanother to a substantial extent.

At the discharge electrode 3, finally, the last charges on thecomposition 8 are removed.

The baffle 9 upstream of the lay-on electron 1 bounds the ion-enrichedspace.

The purpose of the discharge electrode 11 is to prevent charging of theinsulator coat of the conveyor belt 10.

The discharge electrode 12 prevents damage to the silicone layers whenthe coated substrate is removed.

EXAMPLES Example 1

An acrylic adhesive was polymerized in solvents and concentrated in anextruder. In a further extruder, resins, aging inhibitors, and otheradditives were admixed. Coating of the composition took place via a meltpump through a slot die (from Extrusion Dies Inc., USA) with a coatingwidth of 35 cm onto a polypropylene release film, 70 μm thick, withwhich the coating was laid using a contact roller onto atemperature-controllable lay-on roller. In a downstream laminatingstation, a BOPP film 50 μm thick was laminated onto the coated side ofthe first film, which had been provided on both sides with 0.5 g/m²antiadhesive silicone layers. The laminate was then wound up.

In order to charge the composition coat the lay-on electrode used was aneedle electrode (type R130A from Eltex) which was supplied from ahigh-voltage generator (type KNH34/N from Eltex). Additionally, asecond, identical needle electrode (countercharging electrode) wasmounted in the region between the lay-on line of the composition and thetake-off line of the coated substrate from the lay-on roller, andsupplied by a further high-voltage generator (type KNH34/P from Eltex)with high voltage of opposite polarity. The lay-on electrode was loadedwith a negative high voltage of −15.8 kV for a web speed of 75 m/min.The distance of the needle tips from the roller surface, the position ofthe electrode in the running direction of the web, and the angle ofinclination of the electrode to the tangent of the lay-on roller wereoptimized until bubbles were no longer observed between composition andsubstrate. At that point the needle distance was about 5 mm from theroller surface, the position of the electrode was about 8 mm behind thelay-on point in the running direction of the web, and the angle ofinclination to the tangent of the lay-on roller was 90°.

The countercharging electrode was supplied with an opposed, i.e.,positive, high voltage of +13.7 kV, so that the absolute value of theelectrode current was equal to that of the lay-on electrode and thecoated substrate was therefore electrostatically neutralized beforedeparting the roller. The distance of the needle tips of thecountercharging electrode from the roller surface was about 12 mm.

Above the line of detachment of the web from the lay-on roller, however,there was also an active discharge electrode (type R51A from Eltex) fedwith 8 kV oscillating current at a frequency of 50 Hz from a powersupply (Eltec type: ES52).

The aim of the experiment, with a coating speed of 85 m/min and anapplication rate of 85 g/m², was to reduce the damage to theantiadhesive properties of the release film that was found with theabove experimental setup, without observation of bubbles betweencomposition and substrate.

The formation of bubbles was determined in line using a camcorder, astrong light source, and a monitor, with the aid of status pictures atexposure times of between 100 and 1 000 microseconds, and also by theinspection of samples after the web had been halted.

Subsequently, the lay-on roller was wrapped with one ply in each case ofpolyester films of different thickness. At the seam there was overlapbetween the beginning and end of the film. The beginning was fixed tothe roll cylinder using an adhesive film, and the end was fixedcorrespondingly to the beginning of the film. For all of the films,bubbles occurred at the seams between composition and substrate at muchlower web speeds than in the remaining region.

The wraps of film, however, tended toward uncontrolled electrostaticcharging. In the region not covered by the substrate, between thetake-off line of the coated substrate from the lay-on roller and thecontact roller, therefore, an active discharge electrode (type R51A fromEltex) was mounted.

The following web speeds could be reached, without bubbles, withdifferent thicknesses of film wraps:

190 μm PET film 40 m/min  75 μm PET film 75 m/min  50 μm PET film 85m/min  25 μm PET film 85 m/min

Subsequently, the damage to the antiadhesive properties of the releasefilm was determined at the experimental settings of 50 μm PET film and85 m/min, and also at the same speed without covering the lay-on rollerwith film. In this case it was ensured that the seams were not includedin the results.

The damage was determined by the following measurement method.

Measurement of the Release Force

A double-sided test adhesive tape is applied without bubbles to thatside of the release liner that is to be measured, and is pressed on byrolling over it five times with a 2 kg steel roller. The assembly isthen stored in a hot chamber at 70° C. for one week. In order to measurethe peel force (release force), the test tape side facing the releaseliner is fastened to a steel rail. The release liner bonded to the testadhesive tape is then peeled off at an angle of 180° and a speed of 300mm/min. The tensile force (in cN/cm) required to achieve this ismeasured on a tensile testing machine under standardized conditions (23°C., 50% atmospheric humidity).

The values reported are the minimum, the maximum, and the average offive individual measurements.

Release Forces Measured by the Method Indicated

Minimum Maximum Average Undamaged reference sample  8 cN/cm 10 cN/cm  9cN/cm Exposed side of the release film 17 cN/cm 30 cN/cm 24 cN/cm Lay-onroller not covered Lined side of the release film 14 cN/cm 20 cN/cm 17cN/cm Lay-on roller not covered Exposed side of the release film 15cN/cm 23 cN/cm 19 cN/cm Lay-on roller covered with 50 μm PET Lined sideof the release film 13 cN/cm 17 cN/cm 15 cN/cm Lay-on roller coveredwith 50 μm PET

The results show that when the roller is wrapped with an electricalinsulator the release film was damaged to a lesser extent. Wrapping ofthe lay-on roller with relatively thick films, however, reduces the webspeed which can be achieved without bubbles.

Example 2

In this experiment, the same setup as in example 1 was chosen. However,the substrate was guided on a conveyor belt over the lay-on roller. Anadditional active discharge electrode was mounted over the take-off lineof the coated substrate from the conveyor belt, and the dischargeelectrode for the roller wrap was moved, so that it pointed toward thesubstrate-facing side of the conveyor belt.

Used first was a nonconductive belt cloth with woven reinforcement,which was 3 mm thick and already existed on the coating unit. A webspeed of only 20 m/min without bubbles between coating and substrate wasachieved. At higher speeds, in particular, the woven structure in thebelt, despite a smooth surface to the substrate, was reproduced in thepattern of the bubbles between coating and substrate.

Thereafter, instead of the existing belt cloth, the same PET films as inexperiment 1 were used. They were guided over the same deflectorrollers, tensioning rollers, and web-edge control system as the belt.

In terms of the achievable bubble-free web speed and the damage to therelease film, the results of the experiment are identical within thebounds of measurement accuracy.

Example 3

In this experiment, the same setup as in example 1 was chosen. Insteadof the wrapping of the lay-on roller with a film, the lay-on roller wasgiven a bubble-free coating of a PET casting resin. The coating wasapplied in excess. In a following operation, the coating was removed toa thickness of 100 μm, with an accuracy of ±3 μm, and polished.

At this relatively high roller-coating thickness (see example 1) abubble-free web speed of 70 m/min was attained. As in the case of theroller wraps, damage to the release film was reduced.

The following values were achieved by the measurement method specifiedin example 1:

Minimum Maximum Average Undamaged reference sample  7 cN/cm 11 cN/cm  9cN/cm Exposed side of the release film 15 cN/cm 22 cN/cm 18 cN/cm Linedside of the release film 14 cN/cm 18 cN/cm 16 cN/cm

Within the bounds of measurement accuracy, these values correspond tothose with 50 μm PET film wrap in example 1.

1. A process for prod acing a product in web form, said productcomprising at least two layers, said process comprising applying acomposition emerging from an applicator as a layer to a substrate in webform guided over a lay-on roller said applying taking place with anapplication of electrostatic charges, and electrostatically neutralizingthe substrate coated with the composition before the coated substratedeparts the lay-on roller, the lay-on roller being provided with anelectrically insulating coating.
 2. The process as claimed in claim 1,wherein said applicator is configured as a die.
 3. The process asclaimed in claim 1, wherein the composition is electrostatically chargedby means of at least one lay-on electrode.
 4. The process as claimed inclaim 1, wherein as a lay-on electrode two needle electrodes arrangeddirectly following one another in the web direction are used.
 5. Theprocess as claimed in claim 1, wherein the substrate coated with thecomposition is electrostatically neutralized by means of at least onecountercharging electrode before departing the lay-on roller.
 6. Theprocess as claimed in claim 1, wherein the substrate coated with thecomposition is kept electrostatically neutral by means of at least onedischarge electrode on departing the lay-on roller.
 7. The process asclaimed in claim 1, wherein the electrically insulating coating of thelay-on roller is electrostatically neutralized by means of at least onedischarge electrode upstream of a lay-on line of the substrate onto thelay-on roller.
 8. The process as claimed in claim 1, wherein thesubstrate is placed with a contact roller onto the lay-on roller and/oris removed from the lay-on roller with a take-off roller.
 9. The processas claimed in claim 1, wherein a baffle made of electrically insulatingmaterial is mounted in a running direction of a web between anapplicator and a lay-on electrode.
 10. The process as claimed in claim1, wherein the substrate is electrostatically neutralized prior tocoating.
 11. The process as claimed in claim 1, wherein the compositionon the substrate is crosslinked before departing the lay-on roller. 12.The process as claimed in claim 1, wherein the thickness of the coatingis less than 300 μm and/or the thickness deviates by not more than ±20%from the average value over the entire surface of the lay-on roller. 13.The process as claimed in claim 1, wherein the electrically insulatingcoating has antiadhesive properties.
 14. The process as claimed in claim1, wherein the electrically insulating coating is composed of polyester,polytetrafluoroethylene, polyimide, silicone rubber, polypropylene, orcasting resin.
 15. The process as claimed in claim 1, wherein theelectrically insulating coating used is a shrink sleeve which is pulledover the lay-on roller and shrunk.
 16. The process as claimed in claim1, wherein a conductive sleeve with an insulating coating is pulled overthe lay-on roller.
 17. The process as claimed in claim 1, wherein thesubstrate is guided over the lay-on roller on an electrically conductiveconveyor belt which is coated with an electrical insulator.
 18. Theprocess as claimed in claim 1, wherein the substrate is guided over saidlay-on roller on a conveyor belt composed of an electrical insulator.19. The process as claimed in claim 1, wherein the substrate is guidedover a conductive transport means on a electrically insulating auxiliarysheet which is unwound from a bale, and the auxiliary sheet issubsequently wound up into a bale again.
 20. The process as claimed inclaim 1, wherein the substrate is a release liner for an adhesive tapeand/or the composition is an adhesive.
 21. The process as claimed inclaim 1, wherein the substrate is an initial product consisting ofrelease liner, adhesive, and carrier for a double-sided adhesive tapeand the composition is an adhesive.
 22. The process as claimed in claim1, wherein the substrate is a release liner and the coating, consistingof a first adhesive, carrier, and a second adhesive, is applied from atriple-manifold or adaptor die.
 23. The process as claimed in claim 1,wherein said composition comprises acrylic, natural rubber, syntheticrubber or EVA adhesives.
 24. The process as claimed in claim 2, whereinthe die is a slot die, a two-manifold die, a multiple-manifold die or anadaptor die.
 25. The process as claimed in claim 1, wherein the lay-onroller is grounded and/or temperature-controllable.
 26. The process asclaimed in claim 3, wherein the at least one lay-on electrode is locatedabove the lay-on roller in the region of a lay-on line of thecomposition coating.
 27. The process as claimed in claim 4, wherein theneedle electrodes are laterally offset by half the length of a needle.28. The process as claimed in claim 5, wherein the at least one countercharging electrode is located over the lay-on roller in a region betweena lay-on line of the composition coat and a take-off line of the coatedsubstrate.
 29. The process as claimed in claim 6, wherein the dischargeelectrode is located over the lay-on roller in a region of a take-offline of the coated substrate.
 30. The process as claimed in claim 11,wherein the composition on the substrate is crosslinked by at least onecrosslinking method selected from the group consisting of electronbeams, UV rays, visible light and thermally.
 31. The process as claimedin claim 12, wherein the thickness of the coating is between 30 μm and200 μm and/or the thickness deviates by not more than ±5% over theentire surface of the lay-on roller.
 32. The process as claimed in claim31, wherein the thickness of the coating is between 40 μm and 120 μm.33. The process as claimed in claim 18, wherein the conveyor belt has athickness between 20 μm and 300 μm.
 34. The process as claimed in claim33, wherein the conveyor belt has a thickness between 20 μm and 120 μm.35. The process as claimed in claim 19, wherein the auxiliary sheet hasa thickness between 20 μm and 300 μm.
 36. The process as claimed inclaim 35, wherein the auxiliary sheet has a thickness between 20 μm and120 μm.